1. Field
This invention relates generally to food compositions and, more particularly, to baby-food compositions comprising docosahexaenoic acid (DHA) and to methods of using the compositions to improve the health and development of an infant including improving visual acuity.
2. Related Art
Long-chain polyunsaturated fatty acids such as the ω-3 fatty acid, docosahexaenoic acid (DHA), have been shown to be required nutrients for optimal maturation of visual and cortical function in human infants (See, for example, Hoffman et al., Am. J. Clin. Nutr. 57(suppl.):807S–12S, 1993; Makrides et al., Lancet 345:1463–1468, 1995). Although the minimum dietary amount of DHA required by infants has not been unequivocally established, the Food and Agriculture Organization and World Health Organization recommend 40 mg/kg body weight for preterm infants and 20 mg/kg for term infants (FAO/WHO Expert Consultation on Fats and Oils in Human Nutrition, FAO 1994, Rome, pp. 52–55). For term infants this is about 70 mg at birth in about 420 calories and 140 mg at 6 months of age in about 700 calories.
DHA in an infant's diet promotes visual development and leads to enhanced visual acuity. DHA can be provided to breast-fed infants through their mother's milk, which contains a full-complement of both ω-6 and ω-3 polyunsaturated fatty acids (Hoffman et al, 1993, supra; Makrides et al., 1995, supra; Innis et al, Am. J Clin. Nutr 60:347–352, 1994). The concentration of DHA in breast milk can, however, vary depending upon the mother's diet and in addition, many infants are not breast-fed or are breast-fed only for a few weeks and must rely on infant formula and solid baby food for their nutritional requirements. In the past, infant formulas sold in the United States have not contained DHA (Jensen et al., J. Pediatr. 131:200–209, 1997). Nevertheless, feeding an infant a formula supplemented with DHA and arachidonic acid after weaning from breast feeding, has been shown to improve visual acuity (see Birch et al, Am. J. Clin. Nutr 75:570–580, 2002; Hoffman et al., J. Pediatr. 142:669–677, 2003). Semi-solid foods fed to babies have little or no DHA. Intake of fat from such solid foods does not increase plasma DHA levels as does breast feeding (Luukkainen et al., J. Pediatr. Gastroenterol. Nutr. 23: 229–234, 1996).
Thus, it would be desirable to increase the dietary intake of long-chain polyunsaturated fatty acids such as DHA in babies. Sources of DHA that have been added to infant formula to increase the content of DHA include marine oil, extracted egg-yolk lipids and lipids derived from animal tissue phospholipids (U.S. Pat. No. 4,670,285, Uauy, et al., J. Pediatr. 134:612–620, 1994; Makrides, et al., 1995, supra; Carlson, J. Nutr. 126:10925–10985, 1996). However, marine oil tends to have a strong fishy taste and odor and thus is unsuitable for adding to infant formula or solid baby food. In addition, lipids extracted from egg yolk and animal tissue are susceptible to oxidative deterioration. Also, with respect to semi-solid baby-food preparations, production of fish and/or animal oils requires extensive processing, so that the use of such processed oils in a baby-food composition would diverge from the “whole food” and “natural food” concepts of baby food which is popular among caregivers.
One dietary source of DHA in adult foods is whole egg yolk or egg yolk solids. Semi-solid baby-food compositions currently or previously sold commercially in the United States have contained either a small amount of egg-yolk solids, i.e. less than 5%, or a large amount of egg-yolk solids, i.e. about 29% to 30% or more, neither of which is entirely satisfactory as a food source. Baby-food compositions containing less than 5% egg-yolk solids do not provide the amount of nutritional components available in the compositions having higher percentages of egg yolk, whereas baby-food compositions with the higher percentages of egg yolk have not been organoleptically acceptable, i.e., have been extremely poor in taste and, as a result, are no longer commercially available. Indeed, it is well known that infants typically reject cooked egg yolk, apparently because of its strong taste and gritty, mealy texture.
Although hens' eggs ordinarily contain only very low amounts of DHA, hens fed a diet enriched with DHA or DHA precursor can contain about 89–112 mg DHA per egg yolk or about 10 mg DHA per gram of egg-yolk solids. See Table 1, infra. Such DHA-enriched eggs have been developed as sources of DHA for human consumption (Herber et al., Poultry Sci 75:1501–1507, 1996; Oh, U.S. Pat. No. 5,415,879, 1995). Furthermore, infant diets containing DHA-enriched egg yolks increased the amount of DHA in the blood of formula fed infants up to levels similar to those of breast fed infants (Gibson et al., Eggs as a Source of Essential Docosahexaenoic Acid (DHA) in the Diets of Weaning Infants, Rural Industries Research & Development Corporation, 1998). Nevertheless, these investigations provided no suggestion as to how such DHA-enriched eggs might be incorporated into an organoleptically acceptable semi-solid baby-food preparation or one that is shelf-stable and commercially viable.
Thus, there remains a continuing need for a semi-solid, shelf-stable, baby-food composition that can be used to improve visual acuity in an infant. Furthermore, there is a need for a semi-solid baby-food composition that not only can improve visual acuity when fed to an infant, but is also organoleptically acceptable to an infant.